The chemical name of AHU377 is (2R,4S)-5-(Biphenyl-4-yl)-4-[(3-carboxypropionyl)amino]-2-methylpentanoic acid ethyl ester, and the structure is shown as Formula (I):

U.S. Pat. No. 5,354,892A firstly discloses the structure of AHU377, its sodium and the preparation method thereof, but the patent does not disclose crystalline forms of AHU377.
CN102702119A discloses a dual-acting compound LZ696, the structure is shown as Formula (II). The compound takes AHU377 and Valsartan as active ingredients, and the two active ingredients are connected through hydrogen bonds. The patent also discloses a method for preparing LCZ696 by using AHU377 or its salts. LCZ696 is clinically proven to be used for treating various cardiovascular and/or kidney diseases, and LCZ696 was approved in United States in 2015 as trade name “ENTRESTO”.

The inventor summarized the prior art, and discovered that AHU377 was in the form of sticky oil at room temperature. Using AHU377 sticky oil as the starting material is hard to transfer and precisely quantify in the industrial production of LCZ696. According to the prior art, in order to overcome the problem of transfer and precise quantification, AHU377 has to be prepared into a solid salt, but the salt still needs to be broken into AHU377 free acid in the preparation of LCZ696 afterwards. The existing process is not only cumbersome, but also introduces a large number of impurity ions, which are bad for quality control in process.
Based on the problems of prior art, it is of great importance to find a solid form of AHU377, which is suitable for transferring, quantifying and avoiding introducing impurity ions and simplifying the process in the industrial production of LCZ696.